This week, more than 48 million Iranians will get to vote. But not all of them will choose to do so.

Friday's parliamentary election is first national election in Iran since the disputed presidential poll of 2009, which provoked the most serious political crisis in Iran since the 1979 Islamic revolution.

Supporters of the opposition Green Movement claimed that the election was stolen from their candidate Mir Hossein Mousavi. The government sent security forces to put down the mass protests.

No-one expects the 2012 parliamentary elections to trigger a repeat of the scenes of 2009.

Turnout

Human rights organisations report increasing numbers of arrests of activists in the lead-up to the parliamentary vote, while reformists have concluded that there is no point in contesting this election and asked their supporters to stay at home on election day.

In 2009, the strength of the opposition was measured by the size of the street demonstrations.

In 2012, it will be measured by the size of the election turnout. Unsurprisingly, the government is doing its best to encourage everyone to vote.

"There is no doubt that the higher the turnout, the stronger [the] national security," said the Defence Minister, Ahmad Vahidi, in a recent interview with the Irna news agency.

Ruling conservatives even make an appeal for patriotic support - the better the election in Iran, the more it will inspire the Arab Spring in the Middle East, they say.

"Our presence in the election is a model for countries of the Islamic awakening movement and it is the biggest threat to America," said Mehdi Chamran, the head of Tehran's Islamic Council, via the Fars news agency.

Power struggle

In the absence of the reformists, Iran's ruling conservative movement has the election to itself.

Image copyrightReutersImage caption
The supreme leader has a built-in advantage in fights with the president

The poll represents a straightforward fight among conservatives.

Their conflict is easy to summarise - president versus supreme leader.

Ayatollah Ali Khamenei, the supreme leader since 1989, represents the first generation of Islamic rulers in Iran.

He controls many of the country's levers of power and draws particular strength from a close alliance with the powerful Revolutionary Guards, which are tasked with defending the country's Islamic system and providing a counterweight to the regular armed forces.

The President, Mahmoud Ahmadinejad, represents a second generation of Iranian politicians - those who served in the Iran-Iraq war of the 1980s.

Mr Ahmadinejad and his supporters have support among the country's working class and they have sought to reduce the power of Iran's ruling clerics.

The supreme leader and the president were forced to unite in 2009 to defeat the Green Movement. But since then, their alliance has come apart.

The parliamentary election of 2012 marks the first formal chance to assess the strength of each man's support.

IN FACTS AND FIGURES

Population 75m. Eligible voters 48m. Minimum voting age 18 years

Number of seats: 290 seats from 30 provinces. About 60 deputies represent the 10 largest cities

207 Constituencies with 47,000 voting stations

First round 2 March, one quarter of vote is required to win, if not, vote goes to second round. Date unannounced

Number of candidates before vetting: 5,395, after vetting 3,444, ie 36% were disqualified

Disqualifications

In Iran, the supreme leader has a built-in advantage in any fight with the president.

The constitution makes sure that any argument is pre-rigged in the Supreme Leader's favour.

In effect, Ayatollah Khamenei gets to pick which candidates are allowed to run in any election. He does so via a body called the Guardian Council, whose 12 members are appointed by him directly or indirectly.

"The Guardian Council has the responsibility of supervising the elections of the Assembly of Experts, the president of the republic, the Islamic Consultative Assembly [Parliament], and the direct recourse to popular opinion and referenda," says Article 99 of the constitution.

In practical terms, this means that any candidate wishing to run for office has to be approved by the Guardian Council.

The body has plenty of eyes and ears to help make its decisions. It has more than 384 supervisory offices across the country, operating on a budget of $25m.

The Council makes sure that anyone wishing to upend the Islamic system entirely is unable to stand.

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Friday's election will be fought by a number of rival conservative groups

It is also able to disqualify candidates considered threatening to the supreme leader.

Official figures show that 5,395 candidates applied to run in the 2012 parliamentary election. The Guardian Council approved 3,444 of them. Reports suggest that it barred some candidates loyal to the president.

Conservative rivalry

Friday's election will be fought by a number of rival conservative groups.

Supporters of President Ahmadinejad are standing in a number of lists - the Islamic Government Supporters Front, the Young Advisers of the President, the Justice and Compassion Front and the Unity and Justice Front.

The United Principle-ist Front (UPF) is a powerful group which represents the Old Guard and which calls for unity on the basis of Islam and the supreme leader.

The Steadfastness Front (Paydari) represents a group of former Ahmadinejad supporters who have turned against the president.

The respective strength of these groups after the 2012 election will define the balance of power for what may be a much more important vote - the 2013 presidential election.